In railcars, various device units are included in railcar inner spaces, such as a driver's seat. These device units are provided so as to be stored in a storage box (also called a “cover”), such as an interior plate described in PTL 1. For example, a frame is welded to an inner side of such storage box, and the stiffness of the storage box itself is increased by this frame. In addition, the frame also serves as a device receiver at which the device unit is provided. The device unit is fixed to the frame by fastening members, such as bolts, to be arranged in the storage box. The storage box configured as above is welded to a structure of the railcar.